with the exception of the Garmin app being unresponsive, most of the notification issues "should" be fixed once GATT support is added to the Garmin app (if you are currently an insider)
FitBit is rolling out GATT support in beta soon (when? no clue) but no clue if Garmin is planning to soon as well. Hopefully someone supports it when MS "decides" on what they want to do with my Band 2.
I got my HR Saturday... so far have received 0 notifications from my elite x3 besides phone connected/disconnected. Even with the app open. Occasionally the widgets will say "no notifications", or will show upcoming calendar events, but most of the time they all just say "waiting for data". Had a hell of a time getting connect IQ apps to install, but finally did. Also, went to bed with 36% battery and woke to a dead phone.. the culprit - GCM. Before 36% would have gotten me through the night and most of the following day. Really frustrating, was hoping notifications would be at least spotty.
Other than that, I love the device... love the apps, watch faces, widgets. GPS is quick, sleep seems accurate. I might keep it in hopes that notifications eventually work. I love WM and I love my Elite x3, but MS always seems to be a step behind.
**update: I somehow got notifications working today, even with the phone locked they seem to be coming in fairly regularly. I uninstalled/unpaired, but what I think did it was changing GCM app background to always instead of "managed by windows".